es·sen·tial [i sénshəl] adj 1. necessary: of the highest importance for ...of something or somebody We wanted the biography to tell us the essential nature of the man. 3. perfect: being the pure or perfect form or embodiment of...

An essential oil is a concentrated, hydrophobic liquid containing volatile... extracted, such as oil of clove. An oil is "essential" in the sense that it carries a distinctive scent, or essence, of the plant...